Women's Health - April 2005

Folic Acid Shows Promise for Lowering Blood Pressure

Women who take folic acid supplements during their childbearing years to prevent certain birth defects could also be lowering their risk for high blood pressure, according to a study reported in the Journal of the American Medical Association.

Researchers found that women who consumed high levels of the B vitamin from food and supplements significantly reduced their risk of developing hypertension.

"This is the first major study to demonstrate that higher folate intake may be able to lower the risk of developing high blood pressure," says Dr. John P. Forman, a Brigham and Women's Hospital researcher.

"This is especially exciting, given the safety and ready availability of folic acid supplements," adds Dr. Forman, who is the lead author of the study.

Hypertension a Major Health Concern

Hypertension affects an estimated 65 million US adults. Because it typically strikes without symptoms, it is often called the "silent killer." But treatment is critical because elevated blood pressure puts people at increased risk of cardiovascular disease and renal failure.

Folate, also known as folic acid, is necessary for proper cell growth and is thought to lower blood pressure by improving blood vessel function.

Folic acid supplements are widely recommended to women who are pregnant or trying to become pregnant. Studies show folate can decrease the risk for neural tube birth defects such as spina bifida.

In addition to supplements, good dietary sources of folate include leafy green vegetables, such as spinach and turnip greens, fruits, dried beans, and peas.

To see whether there was a link between folate intake and blood pressure, the authors evaluated detailed dietary and health information for more than 150,000 women over eight years.

One group included 62,260 women aged 43 to 70 from the Nurses' Health Study, a prospective study of the risk factors for major chronic disease in women. The other group included 93,803 women, aged 27 to 44, from the Nurses' Health Study II, which involves younger women.

Among younger women who consumed at least 1,000 micrograms per day of folate from dietary and supplemental sources, there was a 46 percent reduction in risk of hypertension compared to women whose folate intake was less than 200 micrograms per day. Older women had an 18 percent reduction in risk of hypertension.

Women who consumed a low amount of folate from foods - less than 200 micrograms per day - but still managed to achieve a total daily folate intake of more than 800 micrograms through supplementation also lowered their risk of developing hypertension. Younger women reduced their risk by 45 percent; older women cut their risk by 39 percent.

Among women who did not use supplements, folate from foods alone did not lower their risk of high blood pressure, the study found.

More Study Needed To Confirm Findings

Dr. Forman cautioned that more research is needed to confirm the findings.

"It is important to emphasize that our study, although providing evidence of the link between folate and blood pressure, is not proof that folate can be used clinically to lower blood pressure," he says.

A large randomized, controlled clinical trial involving women treated with folic acid supplements or a placebo is needed to confirm the findings before any recommendations could be made, he explains.

Dr. Norman M. Kaplan, a clinical professor in the hypertension division at the University of Texas Southwestern Medical Center in Dallas, agrees that the study is observational, as opposed to a more rigorous prospective study comparing outcomes of people taking folate with a control group.

"They clearly took more folate, but we have no idea what else they did," Dr. Kaplan notes.

The authors stopped short of recommending that women boost their folate intake. So what dietary change can they make to avoid high blood pressure?

"The bottom line is people should eat a good diet," Dr. Kaplan says. "They should eat lots of fruits and vegetables, just like their grandmother told them."

Always consult your physician for more information.